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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Is GNAT as good as commercial Ada compilers?
Date: 1997/07/05
Message-ID: <dewar.868108268@merv>#1/1
X-Deja-AN: 254799935
References: <5pl34g$eau$1@news.belwue.de>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-07-05T00:00:00+00:00
List-Id: <comp.lang.ada>


Markus says

<<in the near future I will have to work a lot with GNAT on linux. I wonder
if GNAT is comparable to comercial compilers.

Does it have a source-level debugger ? Are there any features it does not
implement ( Tasking, Garbage collection ), or is it more "buggy" than
commercial ones? WHat about its documentation?
>>


GNAT implements the full Ada 95 language (in fact so far it is the only
Ada 95 technology that does so, including all the special needs annexes).
Of *course* tasking is implemented. GNAT is fully validated on Linux, and
many other targets. 

Garbage collection is another matter, this is not required even in the
annexes (we have had long discussions of this), and GNAT does not implement
garbage collection, although it fully implements finalization and user
defined storage pools which can provide alternative methods of dealing
with autoamtic storage allocation. As far as I know, the only Ada 95
compiler that has garbage collection is the Intermetrics AppletMagic
compiler, but it is a fairly small subset (and does not currently cover
even the full core, omitting for example, tasking).

As to "bugginess", certainly no Ada 95 compiler is bug free, and you
will have to do your own evaluation as to whether GNAT is suitable
for your purposes. We do have a number of customers who have told us
that their software only works on GNAT at this stage, and that other 
Ada95 compilers have not been able to process their sources. On the
other hand, as readers of CLA know, there are certainly cases where
GNAT has a bug, and some other Ada 95 compiler does not have the same
bug (indeed it would be incredible if this were not the case!)

If you are just fiddling around, then an obvious thing to do is to get
hold of the public release of GNAT for Linux (3.09) and see if it works
for you. If you are embarking on a serious large scale project, then you
should consider a more formal evaluation. The advantage of this is that
first, if it is appropriate, you can use a prerelease of GNAT that may
have features that are not yet publicly released, and second, and more
important, you can evaluate our support services. We aim at providing
the best possible support (it is after all our primary product), and many
of our users have found this support critical to their success.

Note that GNAT is the only Ada 95 compiler for Linux, and certainly is
the only validated compiler for Linux (consult the Ada IC listings for
details).

An interesting note is that we are starting to see serious commercial
interest in Ada 95 under Linux, and already have a number of commercially
supported customers for the Linux port, including one who is using Linux
as a host for a VxWorks based GANT cross compiler to the power PC.

As for documentation: You can look at the current documents, they are
available whereever GNAT compilers can be downloaded. See our home page
at www.gnat.com for a list of FTP sites. There are two manuals, the GNAT
users guide, and the GNAT reference manual. Both manuals are being
substantially redone for the 3.10 release, part of our continuing
development, but you can get a good idea of our documentation approach
from the 3.09 versions.

No better advice can be given than to kick the tires yourself here. If
you are interested in a formal evaluation, send email to sales@gnat.com.
Otherwise, go download the 3.09 public version, and take a look. This
version represented the latest and greatest GNAT available at the time
of its release several months ago, it is not a crippled or subset version,
it is the whole technology. You will need to follow the installation
directions carefully, but if you do so, you should be able to install it
yourself -- many others have succeeded (one of the efforts we are  making
for the new 3.10 Linux release is to make the installation much simpler,
at least for Redhat users).

Robert dewar
Ada Core Technologies